Hydrocarbon production from a reservoir or transportation can be affected by the flow rate at which the hydrocarbons can be extracted or moved. Some oil reservoirs contain high viscosity oil and/or hydrocarbons which form wax under certain conditions. Wax deposits are, primarily, from long chain (more than 18 carbon atoms) paraffin hydrocarbons and appear when the temperature of the fluid is below the “cloud” point or waxing temperature. Similarly, gas and gas/condensate production can suffer from hydrate formation at high pressures and low temperatures.
That is, hydrocarbon flow from a production system, such as a well, or through a transportation system, such as a pipeline, can be affected by, amongst other things, both the viscosity of the oil and the build up of wax deposits. It is known to heat the fluids being extracted through the well to increase the flow rate of the fluids. In many cases, the fluids are hot in the reservoir but it is also known to heat the production tubing in the well casing. In many wells, the temperature of the fluids drops, as they approach the wellhead. A natural geothermal heat profile typically gradually reduces in temperature from the bottom of the well towards the wellhead. That is, the temperature of the fluid in the reservoir at the point of extraction (at the perforations) is greater than at the wellhead. In some cases, the decrease in temperature along the length of the well borehole causes the fluids being extracted to be colder than the cloud point and, therefore, wax crystals begin to occur. In addition, the viscosity of the oil in the fluids will also increase. Heating the production pipes helps to maintain the flow rate by minimising wax crystallisation and maintaining a lower viscosity as the reservoir fluids are extracted. Heating of production tubing may also be required after a shut-in period where the static hydrocarbons maybe inclined to form wax depending on their nature. The energy required to re-start the well may be considerable and take a long time, if feasible.
Prior art solutions for heating the fluids being extracted in a well borehole typically rely on resistive heating of heating elements.
The inventor of the present invention has noted that an improved method and system for heating a well can be provided.